Am.  Jour.  Pharm. ") 
Mar.,  1878.  J 
Rapid  Filtration. 
When  the  contents  of  a  stomach  in  cases  of  medico-legal  examina- 
tions are  placed  in  a  bag  of  membrane,  and  this  floated  in  distilled 
water,  the  crystalloids  (neutral  salts,  strychnia,  corrosive  sublimate,  etc.) 
pass  through  the  membrane,  while  the  mucus,  albumen,  etc.,  remain 
behind.  Obviously  again,  there  is  no  chemical  reaction  here.  It  is 
simply  a  separation,  or  in  other  words,  a  dialysis. 
The  greater  the  density  of  liquids  or  gases  on  opposite  sides  of  the 
memaranes  the  more  rapid  will  be  the  dialysis.  We  have  all  bought 
the  fancifully-colored  hydrogen  balloons  sold  on  the  street  corners,  and 
found  them,  to  our  dismay,  grow  smaller  day  by  day,  until  at  last  we 
had  only  a  small  rubber  bag  to  console  ourselves  for  the  loss  of  the 
pretty  toy.  Here  we  have  by  the  law  of  diffusion  just  as  much  a  true 
dialysis  as  we  have  in  the  fact  that  air,  upon  being  drawn  into  the  lung 
of  an  animal,  diffuses  to  the  most  peripheral  air  vesicle,  and  the  carbon 
dioxide,  by  the  same  law,  passes  to  the  external  air. 
As  a  summary  of  the  preceding  remarks,  let  us  say  that  dialysis  is  to 
be  carefully  distinguished  from  filtration,  as  it  is  properly  the  separation 
by  a  natural  law  of  substances  soluble  in  a  common  medium,  but 
possessed  of  different  diffusive  power. 
RAPID  FILTRATION. 
By  Richard  V.  Mattison,  Ph.G. 
[Read  at  the  Alumni  Meeting,  February  7,  1878.) 
It  is  often  a  matter  of  considerable  annoyance  to  the  pharmacist 
desirous  of  dispensing  elegant  preparations,  that  no  means  of  filtering 
cloudy  or  murky-looking  prescriptions  are  at  hand  by  which  this  desid- 
eratum may  be  attained  in  a  few  moments.  It  is  often  desirable  to 
dispense  syrups,  etc.,  that  are  "star  bright,"  and  yet  be  able  to  do  it 
while  the  customer  is  waiting.  While  a  large  number  of  processes  and 
apparatus  are  suited  to  the  wants  of  the  manufacturer,  few  if  any  yet 
published  supply  the  real  want  of  the  dispenser,  viz.,  something  for 
instant  use  at  the  prescription  counter.  To  supply  this  want  I  have 
the  pleasure  of  bringing  forward  to-day  the  following  simple  apparatus. 
It  is  presumed  every  druggist  is  the  possessor  of  a  retort  stand  ;  the 
rings  of  this  are  bound  with  cloth  or  muslin  until  the  central  aperture 
is  of  just  sufficient  size  to  admit  a  globe  of  hard  German  glass,  such  as 
is  used  for  the  ordinary  student's  lamp.    The  reason  we  prefer  a  lamp 
